Abstract: Development of models for the active sites of oxo-transfer molybdoenzymes has been initiated. Suitable models should be capable of oxygen atom transfer to or from the substrate, approach the native coordination unit, and be inert to formation of pox0 Mo (V) dimers. Toward this end, the sterically hindered ligands 2, 6-bis (2, 2-diphenyl-2- hydroxyethyl) pyridine (LN (OH),) and 2, 6-bis (2, 2-diphenyl-2-mercaptoethanyl) pyridine ( ...